Is a pressurized air object heavier?

Is a pressurized air object heavier? In other words, is an object heavier when it contains compressed air than when it's empty? For example, if I have a tire and weigh it before pumping it full of air, will it be heavier after it's pumped up? I say NO. A friend of mine insists it will be heavier once it's filled with air. Who is right?

This is one of those fun topics that no one can agree on, and would require a very accurrate scale that would most likely need to measure down to the milligram.

Note: This would be regular compressed air from an air compressor, not helium or another gas, which might make it lighter (even though I highly doubt a tire full of air would float).

Mark

Reply to
maradcliff
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Your friend.

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Reply to
JohnH

Are you an idiot? They fill propane tanks by weight. What do you think?

Reply to
Toller

He's talking about compressed AIR...not LIQUID propane... ROFL...

Reply to
Jim & Lil

Yes, I realized that as soon as I hit send; though liquid propane is compressed gas propane. and liquid air is compressed air: so it is the same thing only completely different.

A more appropriate example would be comparing the weigh of a full scuba tank and and empty. Don't need a very sensitive scale for that.

Reply to
Toller

I'll just laughing at you. It's all the same thing. The more you put in, the more it weighs.

Bob

Reply to
Bob

What about a pressurized tank of helium? Heavier full of helium than empty?

What if you released the gas from the helium into a large balloon which was attached to the helium tank. Would the balloon at some point lift the helium tank once it was filled with helium from the tank?

Reply to
Bill

Propane is liquid. (LP = Liquid Propane) (Now who is the idiot?) :) Liquid is a big difference from air. However, that website that John posted does prove I am wrong. I just wonder how much weight is added to a 15" tire when 32 lbs of air is added. It can't be a heck of a lot.... I suppose there is a way to figure this from that website, if one was to know how much air went into the tire, but I dont know how much air, and am not good at math. A scale would be easier, but would have to be very accurate.

Mark

Reply to
maradcliff

Of course not, or the tank would float without the balloon......

Mark

Reply to
maradcliff

Well you are wrong on several counts. 1. Of course the tire is heavier with air in it. The size is the same but you add air, so the air inside becomes more dense, period. 2. It is not a fun topic. Whether people agree or not doesn't matter, it is an obvious fact, as obvious as you weighing more if you put pebbles in your pocket.

  1. No you don't need a scale that measures in milligrams, just grams. 4. There is no chance that an auto tire would float in air, regardless of what gas you put in the tire.
Reply to
George E. Cawthon

According to Bill :

Define full. Define empty ;-)

A pressurized tank of gas isn't "full" until you fill it so much that it turns to liquid. The pressures required (depending on the gas), of course, often makes that impractical.

Empty? Do you mean that the tank is a vacuum? Or, full of air you have to displace?

If by empty, you mean "vacuum", then of course, once you add _anything_ to the tank, the weight goes up.

If by empty, you mean full of air, and the adding of helium displaces air, the weight will decrease until you displace all of the air, then it'll start rising again.

Depends on the empty weight of the tank and how much helium was involved, but yes, certainly, it could lift the empty tank.

Reply to
Chris Lewis

Air is a gas that has weight. That weight is 0.080703 pounds per cubic foot. Even helium has weight, 0.011143 pounds per cubic foot, but being about 1/8 the density of air, a balloon of it floats in air just as one lighter liquid will "float" in a heavier one. (vinegar/oil)

It will take someone with more math smarts than I have to calculate the volume of your tire. You could do it by filling it full of water, and draining it and measuring its cubic measurement. Then, when you condense that by 32 psi, the volume of air in the tire increases quite a bit. Therefore it gains weight with each cubic foot of air you put in there.

Any object will float if it weighs less than the water it displaces. I would think that SOME tires and wheels would float if they are a light rim, and possibly a very heavy tire and rim might sink. You would have to do tests to determine that.

But, definitely, a full tire weighs more than an empty one, even though an empty one does have SOME air in there unless it has been removed by a vacuum pump, and then, it would break the bead.

Steve

Reply to
SteveB

I guess someone missed physics class.

Reply to
FDR

Standard air (70 degrees at Sea Level and 0% Relative Humidity) is

13.33 cubic feet per pound. That is at 14.7 Pounds per Square Inch Absolute (PSIA). That is pressure as related to a vacuum. If you pressureize an object with air at 32 PSI Guage, that is (14.7+32) PSIA = 46.7 PSIA. The pressurized air would weigh 3.1769 times as much as Standard Air. Standard Air weighs .075 pounds per cubic foot. The pressurized air weighs .075 * 3.1769 = 0.2382675 pounds per cubic foot. That is a difference of 0.1632675 pounds per cubic foot. So if you had 5 cubic feet of volume in a tire, the difference in weight would be 5 * 0.1632675 = 0.8163375 or almost a pound heavier. Of course if you were using something besides Standard Air as a base, the air would have a different starting weight. For example, colder air would be denser and would weigh more. If your scale could weigh in increments of 1/10 pound, it would show you the difference.

Stretch

Reply to
Stretch

The pressurized object is heavier. Ask anybody who works in a scuba shop... full tanks weigh a good 5-6 lbs more than empty ones.

Your friend is correct.

Reply to
Mortimer Schnerd, RN

There is mass and weight. Adding more air will increase the total mass. In the case of something like a tyre or steel container that will also result in high pressure, it will also make it weigh more. That would apply to any gas. However if you were to replace the contents of a sealed container (like a tyre) currently filled with air with say hydrogen at the same pressure, it will be lighter and have less mass.

In short, you are wrong.

Reply to
Joseph Meehan

Error.. If the balloon expanded enough so that it displaced enough air that the weight of that air (air does have weight) was greater than the weight of the tank and helium, then it would float.

Think of it this way. The full tank weighs more than an empty tank. If you start filling balloons and tie each one onto the tank, each one will try to lift the tank. As the tank is emptied it gets lighter and there are more balloons trying to lift it. Get enough of the them and the tank will be lifted.

Reply to
Joseph Meehan

Your friend. Even air weighs something. You're putting more air into the tire, and it's pretty much staying the same size (hence the air is compressed). Therefore it would be more dense than when empty.

Reply to
Larry Bud

Actually, it's not. A liquid is only a liquid because of temperature and pressure combination. IOW, you can take any gas, compress it enough, and it will become liquid.

You can figure it out if you know the volume of the tire.

Reply to
Larry Bud

"Is a pressurized air object heavier? In other words, is an object heavier when it contains compressed air than when it's empty? For example, if I have a tire and weigh it before pumping it full of air, will it be heavier after it's pumped up? I say NO. A friend of mine insists it will be heavier once it's filled with air. Who is right? "

Sounds to me like we have a long way to go with the "No child left behind" program.

Reply to
trader4

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